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1.
二(2-乙基己基)磷酸(P204)常作为溶液净化除铁的萃取剂,P204-磺化煤油体系中Fe 3+与有机相形成络合能力较强的萃合物,使得Fe 3+反萃比较困难,需采用较高浓度的酸作为反萃剂,但高浓度的酸会破坏有机分子的结构,影响萃取剂循环利用。针对P204-磺化煤油负铁有机相反萃困难的问题,提出利用草酸为反萃剂对负载1g/L铁的P204-磺化煤油有机相的反萃行为进行研究,考察了反萃转速、草酸浓度、反萃温度、反萃时间和相比对Fe 3+反萃率的影响。结果表明:以反萃转速200r/min,草酸0.4mol/L,反萃时间10min,反萃温度40℃,反萃相比1∶1,采用二级逆流萃取方式,铁的反萃率可以达到99%以上;Fe 3+反萃过程是吸热反应,其反应的焓变为81.58kJ/mol,反萃过程符合准一级反应动力学方程,对应活化能为49.5kJ/mol。进一步研究了反萃后P204-磺化煤油有机相对Fe 3+的萃取性能。结果表明:经5次草酸反萃后的P204-磺化煤油有机相萃铁性能几乎不变,对比于高浓度的酸反萃,草酸反萃简化了反萃流程,降低了萃取剂的消耗。 相似文献
2.
Ta 3N 5 was synthesized by nitridation of Ta 2O 5 under NH 3 flow at 700 °C. The catalyst was pure Ta 3N 5 according to X-ray diffraction (XRD), and was about 5 nm in size with a BET specific surface area 52.8 m 2/g. When Ta 3N 5 was added to Fe 3+/H 2O 2 solution (known as Fenton-like system), most Fe 3+ were adsorbed on the Ta 3N 5 surface and could not react with H 2O 2 in the dark, which is different from the general Fenton reaction. Under visible light irradiation, adsorbed Fe 3+ ions were reduced to Fe 2+ rapidly and Fe 2+ were reoxidized by H 2O 2 on the Ta 3N 5 surface, thus a fast Fe 3+/Fe 2+ cycling was established. Kinetics and ESR measurements supported this mechanism. The Ta 3N 5/Fe 3+/H 2O 2 system could efficiently decompose H 2O 2 to generate hydroxyl radicals driven by visible light, which could accelerate significantly the degradation of organic molecules such as N, N-dimethylaniline (DMA), and 2,4-dichlorophenol (DCP). A mechanism was proposed for iron cycling on the basis of experimental results. 相似文献
3.
采用二(2-乙基己基)磷酸酯(P204)-磺化煤油萃取体系从高硫酸氰化尾渣矿浆电解液中富集铁离子,重点研究了P204浓度、相比(O/A)、振荡时间、振荡频率及温度等对Fe 3+萃取率的影响及其萃取过程。研究表明,在P204体积分数为25%、电解液pH为1.5、温度25℃、O/A=1∶1、振荡时间10 min、振荡频率180r/min的条件下,电解液中Fe 3+的单级萃取率可达97.73%以上,饱和萃取容量可达到21.57g/L。Fe 3+在有机相中的萃取富集主要归因于其与P204分子结构中羟基的阳离子交换反应以及磷酰基的配位反应,形成的配合物为FeSO 4A(HA) 3与FeA 3(HA) 3。在草酸1mol/L、O/A=1∶1、振荡时间10min、振荡频率190r/min的条件下,负载有机相中Fe 3+的单级反萃率可达82.64%以上,反萃液中铁主要以[Fe(C 2O 4) 3<... 相似文献
4.
采用实验方法研究了低成本环境友好型添加剂抗坏血酸(AA)对Fe 2+/H 2O 2体系氧化NO气体及其对体系内H 2O 2分解的影响,分析了AA对体系氧化NO能力及H 2O 2分解的影响机制。研究结果表明:AA通过加速Fe 3+向Fe 2+的转化而促进Fe 2+/H 2O 2体系对NO的氧化。[AA] 0:[Fe 2+] 0对体系氧化NO的能力及H 2O 2的分解具有重要影响。综合考虑NO氧化脱除量及H 2O 2消耗量,合理的[AA] 0:[Fe 2+] 0为1/3~1/2。AA的分次添加方式可大幅度提升体系氧化NO气体的能力。研究结果可望为发展基于H 2O 2为氧化剂的烟气NO绿色氧化技术提供理论基础。 相似文献
5.
H 2O 2 used in the photo-Fenton reaction with iron catalyst can accelerate the oxidation of Fe 2+ to Fe 3+ under UV irradiation and in the dark (in the so called dark Fenton process). It was proved that conversion of phenol under UV irradiation in the presence of H 2O 2 predominantly produces highly hydrophilic products and catechol, which can accelerate the rate of phenol decomposition. However, while H 2O 2 under UV irradiation could decompose phenol to highly hydrophilic products and dihydroxybenzenes in a very short time, complete mineralization proceeded rather slowly. When H 2O 2 is used for phenol decomposition in the presence of TiO 2 and Fe–TiO 2, decrease of OH radicals formed on the surface of TiO 2 and Fe–TiO 2 has been observed and photodecomposition of phenol is slowed down. In case of phenol decomposition under UV irradiation on Fe–C–TiO 2 photocatalyst in the presence of H 2O 2, marked acceleration of the decomposition rate is observed due to the photo-Fenton reactions: Fe 2+ is likely oxidized to Fe 3+, which is then efficiently recycled to Fe 2+ by the intermediate products formed during phenol decomposition, such as hydroquinone (HQ) and catechol. 相似文献
6.
Fe 2+/H 2O 2体系可分解产生多种氧化性自由基, 主要包括O 2-·、·OH和HO 2·。本文实验研究了O 2-·、·OH及HO 2·在Fe 2+/H 2O 2体系氧化NO气体过程中的作用。结果表明:在本实验条件下, O 2-·对NO气体的氧化作用不明显;·OH及HO 2·是该体系氧化NO气体的主要活性物质, 其中·OH的氧化作用更大。加快自由基的生成速率可以增强Fe 2+/H 2O 2体系对NO气体的氧化能力, 但O 2的生成速率同时加快。只有少量·OH及HO 2·参与NO的氧化, ·OH与HO 2·之间的快速反应是Fe 2+/H 2O 2体系氧化NO过程中H 2O 2利用率低的主要原因。 相似文献
7.
H 2O 2改性稻杆作为Pb 2+吸附剂,具有改性工艺环保、简单、成本低,以及对Pb 2+吸附率高等特点,是一种优良的改性剂。优化改性工艺,制备优良吸附性能的H 2O 2改性稻杆具有较强的实用价值。详细探讨了改性工艺的影响因素如pH值、H 2O 2用量、Fe 2+/H 2O 2物质的量之比、改性温度、改性时间、稻杆颗粒度和稻杆用量等对改性效果的影响,在单因素实验的基础上,通过正交实验和对比实验对改性工艺进行了进一步优化。得出最适宜的改性工艺为:在100 mL的溶液中,不加FeSO 4的情况下,稻杆用量为3 g,改性pH值为8,H 2O 2用量为稻秆用量的30%,稻杆颗粒度为40目,改性温度为20℃,改性时间为4 h。用2 g H 2O 2改性稻秆处理100 mL 200 mg/L的Pb 2+废水时,对Pb 2+的吸附率为94.45%,吸附容量为9.445 mg/g,表明H 2O 2改性稻秆具有优良的吸附性能。 相似文献
8.
A lost of culturability of bacteria Escherichia coli K12 was observed after exposition to a solar simulator (UV–vis) in a laboratory batch photoreactor. The bacterial inactivation reactions have been carried out using titanium dioxide (TiO 2) P25 Degussa and FeCl 3 as catalysts. At the starting of the treatment, the suspensions were at their “natural” pH. An increase in the efficiency in the water disinfection was obtained when some advanced oxidation processes such as UV–vis/TiO 2, UV–vis/TiO 2/H 2O 2, UV–vis/Fe 3+/H 2O 2, UV–vis/H 2O 2 were applied. The presence of H 2O 2 accelerates the rate of disinfection via TiO 2. The addition of Fe 3+ (0.3 mg/l) to photocatalytic system decreases the time required for total disinfection (<1 CFU/ml), for TiO 2 concentrations ranging between 0.05 and 0.5 g/l. At TiO 2 concentrations higher than 0.5 g/l the addition of Fe 3+ does not significantly increase the disinfection rate. The systems: Fenton (H 2O 2/Fe 3+/dark), H 2O 2/dark, H 2O 2/TiO 2/dark showed low disinfection rate. The effective disinfection time (EDT 24) was reached after 60 and 30 min of illumination for the Fe 3+ and TiO 2 photoassisted systems, respectively. EDT 24 was not reached for the system in the absence of catalyst (UV–vis). The effect on the bacterial inactivation of different mixture of chemical substance added to natural water was studied. 相似文献
9.
Fe 2+的再生直接决定Fenton体系产生的能力。选取羟胺、对苯二酚、对苯醌、亚硫酸钠4种典型添加剂,通过分析不同改性Fenton体系中Fe 2+浓度、H 2O 2浓度、氧化还原电极电位(ORP),揭示了Fe 2+再生机制的差异,并进一步分析了不同添加剂与体系中H 2O 2及·OH的反应情况。结果表明:NH 2OH能快速使Fe 2+再生,但伴随其消耗,Fe 2+浓度不断降低。对苯二酚、对苯醌具有相似效果,两者均可大大强化Fe 2+的再生。与NH 2OH不同,两者在体系中可迅速建立醌循环,持续还原Fe 3+,且以两种物质或其组合均可建立循环。与上述机理均不同,Na 2SO 3会先与·OH及H 2O 2反应,因而不能有效还原Fe 3+。实验还发现添加剂均存在与·OH的反应,其中Na 2SO 3还会消耗H 2O 2。 相似文献
10.
掌握Fe 2+/H 2O 2体系O 2的生成路径,可为避免H 2O 2无效分解,开发经济高效的Fe 2+/H 2O 2体系利用技术指明方向。采用添加自由基捕获剂的方法,探究Fe 2+/H 2O 2体系内各种自由基对O 2生成速率的影响,进而确定O 2的生成路径。结果表明:Fe 2+/H 2O 2体系内不会产生大量O 2-·,O 2-·不是生成O 2的主要反应物质;O 2-·被全部捕获后,体系中仍产生大量O 2-·,但此时无O 2生成,证明生成O 2的反应由·OH和HO 2·两种自由基直接参与。分析认为反应·OH+HO 2·-H 2O+O 2是体系内O 2生成的主要路径。控制Fe 2+/H 2O 2体系定向生成·OH,抑制HO 2·的产生,是提高Fe 2+/H 2O 2体系中H 2O 2利用率的有效手段。 相似文献
11.
Hydrogen fuel has been embraced as a potential long-term solution to the growing demand for clean energy. A membrane-assisted separation is promising in producing high-purity H 2. Molecular sieving membranes (MSMs) are endowed with high gas selectivity and permeability because their well-defined micropores can facilitate molecular exclusion, diffusion, and adsorption. In this work, MXene nanosheets intercalated with Ni 2+ were assembled to form an MSM supported on Al 2O 3 hollow fiber via a vacuum-assisted filtration and drying process. The prepared membranes showed excellent H 2/CO 2 mixture separation performance at room temperature. Separation factor reached 615 with a hydrogen permeance of 8.35 × 10 −8 mol·m −2·s −1·Pa −1. Compared with the original Ti 3C 2T x/Al 2O 3 hollow fiber membranes, the permeation of hydrogen through the Ni 2+-Ti 3C 2T x/Al 2O 3 membrane was considerably increased, stemming from the strong interaction between the negatively charged MXene nanosheets and Ni 2+. The interlayer spacing of MSMs was tuned by Ni 2+. During 200-hour testing, the resultant membrane maintained an excellent gas separation without any substantial performance decline. Our results indicate that the Ni 2+ tailored Ti 3C 2T x/Al 2O 3 hollow fiber membranes can inspire promising industrial applications. 相似文献
12.
Nafion supported catalytic membranes were found to be effective in the partial oxidation of propane to oxygenates with H 2O 2 in the presence of Fe 2+ under mild conditions. The influence of [Fe 2+] and [H 2O 2] on the reaction rate and product distribution in the temperature range 80–110°C has been ascertained. A reaction pathway involving the electrophilic activation of propane on superacid sites and subsequent reaction of the activated propane molecules with OH radicals generated by Fe 2+/H 2O 2 Fenton system is discussed. 相似文献
13.
Alachlor, atrazine and diuron dissolved in water at 50, 25 and 30 mg/L, respectively were photodegraded by Fe 2+/H 2O 2, Fe 3+/H 2O 2, TiO 2 and TiO 2/Na 2S 2O 8 treatments driven by solar energy at pilot-plant scale using a compound parabolic collector (CPC) photoreactor. All the advanced oxidation processes (AOPs) employed mainly compared the TOC mineralisation rate to evaluate treatment effectiveness. Parent compound disappearance, anion release and oxidant consumption are discussed as a function of treatment time. The use of Fe 2+ or Fe 3+ showed no influence on the reaction rate under illumination and the reaction using 10 or 55 mg/L of iron was quite similar. TiO 2/Na 2S 2O 8 showed a quicker reaction rate than TiO 2 and a similar rate compared to photo-Fenton. The main difference found was between TiO 2/Na 2S 2O 8 and photo-Fenton, detected during atrazine degradation, where pesticide transformation into cyanuric acid was confirmed only for TiO 2/Na 2S 2O 8. 相似文献
14.
在浸没式循环撞击流反应器中,以氨水为沉淀剂,用七水合硫酸亚铁和六水合三氯化铁为原料,采用共沉淀法制备了纳米四氧化三铁粒子。考察了搅拌转速、亚铁与三价铁物质的量比、反应温度和溶液pH对所得纳米四氧化三铁的分散性和粒径的影响。采用傅里叶红外光谱仪、透射电镜、X射线衍射仪等对制得的纳米粒子的结构和性能进行了表征。结果表明:用撞击流反应器制备纳米四氧化三铁粒子的最佳工艺条件:亚铁与三价铁物质的量比为1 ∶1,反应温度为40 ℃,搅拌转速为1 600 r/min,以氨水作沉淀剂,最佳pH控制在11.0左右。在上述条件下,可以制备出分散性好、纯度高、平均粒径为10 nm的四氧化三铁粒子。 相似文献
15.
Decolorization of reactive brilliant red X-3B was studied by using an Fe–Ce oxide hydrate as the heterogeneous catalyst in the presence of H 2O 2 and UV. The decolorization rate was in the order of UV–Fe–Ce–H 2O 2 > UV–Fe 3+–H 2O 2 > UV–H 2O 2 > UV–Fe–Ce ≥ Fe–Ce–H 2O 2 > Fe–Ce. Under the conditions of 34 mg l −1 H 2O 2, 0.500 g l −1 Fe–Ce, 36 W UV and pH 3.0, 100 mg l −1 X-3B could be decolorized at efficiency of more than 99% within 30 min. The maximum dissolved Fe during the reaction was 1 mg l −1. From the fact that the decolorization rate of the UV–Fe–Ce–H 2O 2 system was significantly higher than that of the UV–Fe 3+–H 2O 2 system at Fe 3+ = 1 mg l −1, it is clear that the Fe–Ce functioned mainly as an efficient heterogeneous catalyst. UV–vis, its second derivative spectra, and ion chromatography (IC) were employed to investigate the degradation pathway. Fast degradation after adsorption of X-3B is the dominant mechanism in the heterogeneous catalytic oxidation system. The first degradation step is the breaking down of azo and CN bonds, resulting in the formation of the aniline- and phenol-like compounds. Then, the breaking down of the triazine structure occurred together with the transformation of naphthalene rings to multi-substituted benzene, and the cutting off of sulphonic groups from the naphthalene rings. The last step includes further decomposition of the aniline structure and partial mineralization of X-3B. 相似文献
16.
Field disinfection of water in a large solar compound parabolic collector (CPC) photoreactor (35–70 l) was conducted at 35 °C by different photocatalytic processes: sunlight/TiO 2, sunlight/TiO 2/Fe 3+, sunlight/Fe 3+/H 2O 2 and compared to the control experiment of direct sunlight alone. Experiments were carried out using a CPC and natural water spiked with E. coli K 12. Under these conditions, total disinfection by bare sunlight irradiation was not reached after 5 h of treatment; and bacterial recovery was observed during the subsequent 24 h in the dark. The addition of TiO2, TiO2/Fe3+ or Fe3+/H2O2 to the water accelerates the bactericidal action of sunlight, leading to total disinfection by solar-photocatalysis. No bacterial regrowth was observed during 24 h after stopping sunlight exposure. For some samples, the decrease of bacteria continues in the dark. A “residual disinfection effect” was observed for these samples before reaching the total inactivation. The effective disinfection time (EDT24), defined as the treatment time required to prevent any bacterial regrowth during the subsequent 24 h in the dark, after stopping the phototreatment, was reached in the presence but not in the absence of different photocatalytic systems. EDT24 was 2 h 30 min, 2 h and 1 h 30 min for sunlight/TiO2, sunlight/TiO2/Fe3+ and sunlight/Fe3+/H2O2 systems, respectively. The post irradiation events observed when the phototreated water is poured into an optimal growth medium are also discussed. 相似文献
17.
以亚甲基蓝(MB)作为目标污染物,实验研究了Fe 2+/H 2O 2体系降解MB的活性物质,明确了主要反应条件对MB降解的影响特性。结果表明:HO 2?没有直接降解MB的能力;Fe 2+/H 2O 2体系对MB的降解能力主要来自于?OH;Fe 2+/H 2O 2体系降解MB可分为快速反应阶段和匀速反应阶段。快速反应阶段的MB降解率随温度升高而下降。体系对MB降解能力随H 2O 2初始浓度增加呈现先升高后减弱的趋势,本实验条件下,最佳H 2O 2初始浓度为5 mmol·L -1。体系对MB降解能力随Fe 2+初始浓度的增加而单调增加。MB降解速率随MB初始浓度的增加而增加,但MB降解率随其初始浓度呈现先增大后减小的趋势。保证?OH生成速率及其有效利用是提高体系氧化能力及H 2O 2利用率的关键。 相似文献
18.
The catalytic behavior of the Fe 3+/Fe 2+ system in the electro-Fenton degradation of the antimicrobial drug chlorophene has been studied considering four undivided electrolytic cells, where a Pt or boron-doped diamond (BDD) anode and a carbon felt or O 2-diffusion cathode have been used. Chlorophene electrolyses have been carried out at pH 3.0 under current control, with 0.05 M Na 2SO 4 as supporting electrolyte and Fe 3+ as catalyst. In these processes the drug is oxidized with hydroxyl radical (OH) formed both at the anode from water oxidation and in the medium from electrochemically generated Fenton's reagent (Fe 2+ + H 2O 2, both of them generated at the cathode). The catalytic behavior of the Fe 3+/Fe 2+ system mainly depends on the cathode tested. In the cells with an O 2-diffusion cathode, H 2O 2 is largely accumulated and the Fe 3+ content remains practically unchanged. Under these conditions, the chlorophene decay is enhanced by increasing the initial Fe 3+ concentration, because this leads to a higher quantity of Fe 2+ regenerated at the cathode and, subsequently, to a greater OH production from Fenton's reaction. In contrast, when the carbon felt cathode is used, H 2O 2 is electrogenerated in small extent, whereas Fe 2+ is largely accumulated because the regeneration of this ion from Fe 3+ reduction at the cathode is much faster than its oxidation to Fe 3+ at the anode. In this case, an Fe 3+ concentration as low as 0.2 mM is required to obtain the maximum OH generation rate, yielding the quickest chlorophene removal. Chlorophene is poorly mineralized in the Pt/O 2 diffusion cell because the final Fe 3+–oxalate complexes are difficult to oxidize with OH. These complexes are completely destroyed using a BDD anode at high current thanks to the great amount of OH generated on its surface. Total mineralization is also achieved in the Pt/carbon felt and BDD/carbon felt cells with 0.2 mM Fe 3+, because oxalic acid and its Fe 2+ complexes are directly oxidized with OH in the medium. Comparing the four cells, the highest oxidizing power regarding total mineralization is attained for the BDD/carbon felt cell at high current due to the simultaneous destruction of oxalic acid at the BDD surface and in the bulk solution. 相似文献
19.
Oxidative reactions of phenol and chlorobenzene with electrogenerated Fenton's reagent, Fe 2+ + H 2O 2, were investigated. The electrogeneration of H 2O 2 and the regeneration of Fe 2+ were performed at a graphite cathode. Results are compared for conventional vs. electrogenerated Fenton's reagent. It was found that the conversion of chlorobenzene was substantially greater by the electrochemical method than the conventional system. The rates of H 2O 2 generation were dependent on solution pH; electrogeneration was favored at low pH, while the opposite was the case for the hydroxylation of the organics. The hydroxylation products of phenol with electrogenerated Fenton's reagent included hydroquinone, catechol and resorcinol. For chlorobenzene, a hydroxylated product (p-chlorophenol) and a dehalogenated product (phenol) were obtained. The rates of phenol and chlorobenzene hydroxylation were dependent on pH, and concentrations of F 2+ and H 2O 2. Results indicated that the electrochemical system provided an efficient way to regenerate Fe 2+ 相似文献
20.
利用嗜酸性氧化亚铁硫杆菌将含硫酸亚铁废溶液中的Fe 2+氧化成Fe 3+后用于脱除H 2S,同时实现了含硫酸亚铁废溶液的循环利用和H 2S的脱除。而溶解性Fe 3+较高的生成量是保证该处理系统连续高效运行的关键因素。但在充足氮源和K +条件下大量Fe 3+以黄铁矾沉淀形式存在。因此,本文通过控制氮源种类及投加浓度,减少沉淀生成,增大溶解性Fe 3+生成量,以期提高H 2S的去除效率。结果表明(NH 4) 2HPO 4可替代以往研究中的(NH 4) 2SO 4作为氮源,确定适宜菌体生长的氮源浓度范围为0.33~1 g·L -1。在1 g·L -1 (NH 4) 2HPO 4条件下细菌生长无明显停滞期、Fe 2+平均氧化速率为0.221~0.229 g·(L·h) -1,Fe 3+生成量为7.62~7.72 g·L -1,沉淀量为1.17 g·L -1,因此确定(NH 4) 2HPO 4为1 g·L -1时最能保证H 2S的脱除效率。为降低工艺成本,最低可采用0.33 g·L -1为运行浓度。该优化方案不仅保证了菌体的Fe 2+氧化活性,而且有效地减少了菌体培养过程中沉淀的产生,获得了较高的Fe 3+生成量和增速,为使用含硫酸亚铁废溶液处理H 2S的工艺条件优化提供了依据。 相似文献
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